Fuel injection valve for internal combustion engines

ABSTRACT

A fuel injection valve for internal combustion engines, having a valve member guided axially displaceably, counter to a closing force, in a blind bore of a valve body. The valve member on an end toward the combustion chamber has a conical valve sealing face, with which the valve sealing face cooperates with a conical valve seat face on the inward-projecting closed end of the blind bore. A blind bore region, adjoins the conical valve seat face downstream, from which region injection openings lead into the combustion chamber of the engine. The blind bore wall region that receives the injection openings is embodied conically, and the injection openings have a certain minimum spacing from an upper and a lower end of this conical blind bore wall region.

PRIOR ART

The invention is based on a fuel injection valve for internal combustionengines. In one such fuel injection valve, known from German published,nonexamined patent application DE 42 02 752, a valve member is guided ina blind bore of a valve body, axially displaceably counter to a closingforce. The valve member, lower end toward the combustion chamber, has aconical valve sealing face, with which it cooperates with a conicalvalve seat face on the inward-projecting closed end of the blind bore.Between the valve seat face and the valve sealing face, an opening crosssection is formed at which a flow of fuel from a high-pressure fuelchamber into the closed end of the blind bore can be controlled. Theconical valve seat face of the known valve is downstream by a furtherblind bore wall region, from which a plurality of injection openingslead away into the combustion chamber of the engine to be supplied.

The known fuel injection valve has the disadvantage that the wall regionof the blind bore adjoining the valve seat face is embodiedcylindrically and furthermore in radius form, so that even slightproduction variations in the axial disposition of the injection openingsresult in different inlet angles at the injection openings, which alterthe inflow behavior, the flow inside the injection opening, and thus theinjection stream characteristic at the outlet openings. However, sincethe stream characteristic at all the injection openings has very greatsignificance in terms of optimal stream preparation and fuel combustionin the combustion chamber of the engine, the known fuel injection valvesno longer meet the high demands made of modern fuel injection valves interms of emissions-optimized stream preparation and combustion insidethe engine.

ADVANTAGES OF THE INVENTION

The fuel injection valve according to the invention for internalcombustion engines, has an advantage over the known valve that withrespect to their placement, the injection openings have a high tolerancefor production variation, so that particularly deviations in position inthe axial direction of the injection valve initially have no influencewhatever on the flow conditions at the injection openings. This relativeindependence of the axial positional tolerance of the injection openingsis attained according to the invention by means of the conicalembodiment of the region of the blind bore of the fuel injection valvethat receives the injection openings. At their inlet openings, theinjection openings have a predetermined minimum spacing from the upperand lower ends of the conical blind bore wall region; the spacingbetween the upper end of an inlet opening of the injection opening andan upper, upstream boundary edge of the conical blind bore wall regionis the size of at least half the diameter of the injection opening.Advantageously, the spacing between the lower end of an inlet opening ofthe injection opening and a lower, downstream boundary edge of theconical blind bore wall region is the size of at least one-quarter ofthe diameter of the injection opening. This assures that even if thereis a slight offset among the individual injection openings in the axialdirection of the fuel injection valve from one another, the inlet anglesat all the injection openings will always constantly have the samevalue, so that the injection streams can be embodied uniformly. It isadvantageous that the valve seat face and the conical blind bore wallregion following the valve seat face downstream have different coneangles. The conical blind bore wall region and the valve seat face canadjoin one another directly, but it is also possible as an alternative,as shown in the exemplary embodiment, to provided a cylindrical wallsegment region between these two faces. The transition from this wallsegment face to the conical blind bore wall region that receives theinjection openings is advantageously rounded off in a streamlined waywith a radius. It is possible to dispose all the injection openings inthe same row of injection ports in a single conical face, but it is alsopossible to embody the conical blind bore wall face with a plurality ofsuccessive conical faces; one row of injection ports can then bedisposed in each conical face. Once again, certain minimum spacings ofthe inlet openings of the injection openings from the ends of theconical faces should be provided.

A further advantage of the fuel injection valve of the invention is thedisposition of the injection opening, embodied as an injection bore, atan acute angle β from the wall surface of the conical blind bore wallupstream of the injection opening. This angle of inclination β betweenthe longitudinal axis of the injection bore and the conical blind borewall region located upstream of the injection bore should also beembodied as <90°. This angular range makes a sharp deflection inletangle in the fuel flow possible at the top of the inlet opening of theinjection bore; the fuel flow is thus made turbulent and generatescavitation, so that within the injection bore an injection stream formswhose flow profile is embodied such that at the outlet of the injectionbore it is atomized as quickly as possible, which results in good streampreparation in the engine combustion chamber and optimal ensuing fuelcombustion.

On the assumption that the sum between the cone angle Ψ, formed betweenthe longitudinal axis of the fuel injection valve and the longitudinalaxis of the injection bore, and the aforementioned inlet angle β and theangle alpha enclosed between the longitudinal axis of the injectionvalve and the conical blind bore wall are 180°, it is now possible indesigning the fuel injection valve, at a predetermined inlet angle β anda projected inlet face at the inlet opening of the injection bore, andat a cone angle T predetermined by the desired stream position, tocalculate the cone angle α of the conical blind bore wall face at theinjection openings in such a way that an optimal velocity profile of theinjection stream, or an optimal velocity profile of the injectionstream, or an optimal stream characteristic of the injection stream, atthe outlet of the injection opening can be attained. Thus compared withthe known fuel injection valves at predetermined cone angles Ψ, an inletangle β<90° is established by way of the constructive design of the coneangle α of the conical blind bore wall face. In this way, very stableinflow conditions for all the injection openings can be established,which also meet the high demands made of new modern fuel injectionsystems, such as pump-line nozzles, unit fuel injectors, and common railsystems. In addition, compared with rounding of the inlet edges of theinjection port, high production tolerances are obtained, so that verystable fuel injection stream geometries at all the injection openingscan be attained here.

Further advantages and advantageous features of the subject of theinvention can be learned from the specification, drawing and claims.

BRIEF DESCRIPTION OF THE DRAWING

One exemplary embodiment of the fuel injection valve of the inventionfor internal combustion engines is shown in the drawing and described infurther detail in the ensuing description. FIG. 1 is a longitudinalsection through the injection end of an otherwise known fuel injectionvalve, having the design according to the invention of the closed end ofthe blind bore.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The exemplary embodiment of the fuel injection valve according to theinvention for internal combustion engines, which is shown in FIG. 1 interms only of its part toward the combustion chamber that is essentialto the invention, has a piston-like valve member 1, which is guidedaxially displaceably in a blind bore 3 of a valve body 5. On its lowerend toward the combustion chamber, the valve member 1 has a conicalvalve sealing face 7, with which the sealing face cooperates with aconical valve seat face 9 on the inward-projecting closed end of theblind bore 3. This conical valve seat face 9 is adjoined downstream, inthe direction of the closed end of the blind bore 3, by a cylindricalwall segment 11, which is adjoined of the remote from the valve seatface 9 and downstream, cylindrical wall segment 11 by a furtherconically embodied blind bore wall region 13, which discharges directlyat the bottom 15 of the blind bore 3. The cross-sectional transitionsbetween the conical blind bore wall region 13 and the cylindrical wallsegment 11 and the bore bottom 15 are rounded off via a radius R. Inaddition, injection openings 17 lead away from the conical blind borewall face 13 and discharge at the circumference of the valve body 5 intothe combustion chamber of the engine to be supplied. The inlet openings19 of the injection openings 17, when the fuel injection valve is closedor in other words when the valve sealing face 7 of the valve member 1rests on the valve seat face 9 in a closed position, not shown, in whicha closing spring, also not shown, keeps the valve member 1 in contactwith the valve seat 9, are not sealingly covered by the valve sealingface 7 of the valve member 1, and thus the fuel injection valve of theinvention is embodied as a so-called blind bore nozzle. The inletopenings 19 have a predetermined minimum spacing from theupstream-pointing upper end of the conical blind bore wall region 13 andfrom its lower, downstream-pointing end. The spacing between the upper,upstream-pointing boundary edge of the injection opening 19 and anupper, upstream boundary edge 21 of the conical blind bore wall region13 should have the size of at least half the diameter of the injectionopening 17. The spacing between the lower, downstream-pointing edge ofthe inlet opening 19 of the injection opening 17 and a lower, downstreamboundary edge 23 of the conical blind bore wall region 13 should amountto at least one-fourth the diameter of the injection opening 17. Inaddition, the cone angles of the valve seat face 9 and the conical blindbore wall face 13 should have different cone angles.

For the sake of the sharpest possible stream deflection at the entranceto the inlet opening 19 of the injection opening 17, an inlet angle β atthe top of the inlet opening 19 of the injection opening 17 between itsbore axis and the conical blind bore wall face 13 should be embodied asless than 900. In this way, when the fuel flows over from the blind bore3 into the injection opening 17 at the top of the inlet opening 19,reverse eddies and also cavitation are generated, which make the highestpossible stream turbulence, and thus at the outlet of the injectionopening 17 the atomization of the injection stream as close as possibleto the nozzle, possible. From the known relationship that the sum of thecone angle Ψ, which is formed between the longitudinal axis of the fuelinjection valve and the axis of the injection opening 17, and a coneangle α, which is enclosed between the longitudinal axis of the fuelinjection valve and the conical blind bore wall 13, and the inlet angleβ are 180°, the following nozzle construction rule can be derived. Aninlet angle β that is optimized in terms of streamlining ispredetermined and then, as a function of a predetermined cone angle Ψ,it determines the necessary angle for the cone angle α. The value of thecone angle Ψ is likewise predetermined by the desired stream position ofthe injected fuel in the engine combustion chamber. In this way, by wayof a precisely defined blind bore geometry, an optimal stream embodimentand characteristic in the combustion chamber of the engine can beattained.

With the fuel injection valve of the invention, it is thus possible, byway of a precisely defined blind bore geometry, to make the arrangementof individual injection openings in the valve body 5 highly insensitiveto tolerances; even if there are slight deviations in position, auniform stream pattern at the outlet openings of all the injectionopenings is also assured.

The foregoing relates to a preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A fuel injection valve for internal combustionengines, comprising a valve member (1) which is guided axiallydisplaceably, counter to a closing force, in a blind bore (3) of a valvebody (5), said valve member on an end toward the combustion chamber hasa conical valve sealing face (7), with which the conical sealing facecooperates with a conical valve seat face (9) on an inward-projectingclosed end of the blind bore (3), and having a blind bore region,adjoining the conical valve seat face (9) downstream, from the blindbore region injection openings (17) that lead into the combustionchamber of the engine, the blind bore wall region (13) that receives theinjection openings (17) is embodied conically, and the injectionopenings (17) have a certain minimum spacing from an upper and a lowerend (21, 23) of this conical blind bore wall region (13), a cylindricalwall segment (11) is provided between the conical valve seat face (9)and the conical blind bore wall region (13) that receives the injectionopenings (17), and the transitional surface between the cylindrical wallsegment (11) and the conical blind bore wall region (13) is rounded offwith a radius R.
 2. The fuel injection valve of claim 1, in which thespacing between the upper end of an inlet opening (19) of the injectionopening (17) and an upper, upstream boundary edge (21) of the conicalblind bore wall region (13) are the size of at least half a diameter ofthe injection opening (17).
 3. The fuel injection valve of claim 1, inwhich the spacing between the lower end of an inlet opening (19) of theinjection opening (17) and a lower, downstream boundary edge (23) of theconical blind bore wall region (13) is a size of at least one-quarter ofa diameter of the injection opening (17).
 4. The fuel injection valve ofclaim 1, in which the conical valve seat face (9) and the conical blindbore wall region (13) following the conical valve seat downstream havedifferent cone angles.
 5. The fuel injection valve of claim 1, in whichthe injection openings (17) are embodied as injection bores, whoselongitudinal axis has an inlet angle β<90° relative to the wall face ofthe conical blind bore wall region 13 upstream of the injection opening17.